1. Field of the Invention
The present invention relates to a control apparatus for an internal combustion engine and to an engine system. In particular, the invention relates to fuel injection control for an internal combustion engine having a first fuel injection mechanism (in-cylinder injector) injecting fuel toward the inside of a cylinder and a second fuel injection mechanism (intake manifold injector) injecting fuel toward the inside of an intake manifold and/or an intake port.
2. Description of the Background Art
A configuration of an internal combustion engine is known that has both of an in-cylinder injector injecting fuel directly to a combustion chamber of the engine and an intake manifold injector injecting fuel to an intake port. A configuration is disclosed (for example in Japanese Patent Laying-Open No. 2002-364409) according to which such an internal combustion engine as described above is operated to carry out homogeneous combustion by fuel injection from the in-cylinder injector in addition to fuel injection from the intake manifold injector, for the purpose of suitably preventing the in-cylinder injector from being kept at a high temperature.
Further, Japanese Patent Laying-Open No. 2001-336439 discloses the technique of appropriately setting the ratio between the quantity of fuel to be injected into the cylinder and the quantity of fuel to be injected into the intake manifold, taking into account the state of atomization of injected fuel in the cylinder of an internal combustion engine similar to the aforementioned one.
For the internal combustion engine as described above, in order to achieve a satisfactory operating state of the engine, it is important to control setting of the fuel injection ratio between the in-cylinder injector and the intake manifold injector. Therefore, in order to appropriately operate the engine under various conditions, it is desirable to control the fuel injection ratio in consideration of not only conditions concerning the in-cylinder injector as disclosed in the above-referenced publications, but also conditions concerning the intake manifold injector.